September weather forecast and climate
Mill Valley, CA

Weather in September

September, the first month of the autumn, in Mill Valley, is also an agreeable month, with average temperature fluctuating between 56.1°F (13.4°C) and 72.3°F (22.4°C).

Temperature

With an average high-temperature of 72.3°F (22.4°C) and an average low-temperature of 56.1°F (13.4°C), September is the warmest month.

Humidity

In Mill Valley, the average relative humidity is 71%.

Rainfall

Months with the least rainfall are June through September Rain falls for 1.7 days and accumulates 0.04" (1mm) of rain.

Daylight

In September, the average length of the day is 12.4h.

Sunshine

In September, the average sunshine in Mill Valley is 10.4h.

UV index

April, June through September, with an average maximum UV index of 5, are months with the highest UV index in Mill Valley, California. A UV Index of 3 to 5 symbolizes a moderate threat to health from unsafe exposure to the UV radiation for average individuals.
Note: The daily maximum UV index of 5 interpret into the following advice:
Take precautions - Protection against the skin and eye damage is obliged. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. A wide-brim hat offers excellent sun protection for eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure. Tightly woven, loose-fitting clothes provide additional protection from the Sun.
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FAQ

What is the warmest month in Mill Valley?

September is the warmest month in Mill Valley, with an average high-temperature of 72.3°F (22.4°C) and an average low-temperature of 56.1°F (13.4°C).

What is the temperature in September in Mill Valley?

In Mill Valley, in September, the average high-temperature is 72.3°F (22.4°C), and the average low-temperature is 56.1°F (13.4°C).

What is the average humidity in September in Mill Valley?

In Mill Valley, the average relative humidity in September is 71%.

How much does it rain in Mill Valley in September?

In September, in Mill Valley, the rain falls for 1.7 days. Throughout September, 0.04" (1mm) of precipitation is accumulated.

What is the driest month in Mill Valley?

June through September are months with the least rain in Mill Valley when the rain falls for 1.7 days and typically aggregates up to 0.04" (1mm) of rain.

What is the average length of the day in September in Mill Valley?

The average length of the day in September is 12.4h.

How long on average sun shines in September in Mill Valley?

The average sunshine in September in Mill Valley, California, is 10.4h.

When is the highest UV index in Mill Valley?

Months with the highest UV index are April, June through September, with an average maximum UV index of 5.

What is the UV index reading in September in Mill Valley?

The average daily maximum UV index in September in Mill Valley, California, is 5. A UV Index value of 3 to 5 symbolizes a medium health risk from unprotected exposure to the UV radiation.

Average temperature in September
Mill Valley, CA

Average temperature in September - Mill Valley, CA
  • Average high temperature in September: 72.3°F

The warmest month (with the highest average high temperature) is September (72.3°F).
The month with the lowest average high temperature is December (55.4°F).

  • Average low temperature in September: 56.1°F

The month with the highest average low temperature is September (56.1°F).
The coldest month (with the lowest average low temperature) is December (45.3°F).

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Average pressure in September
Mill Valley, CA

Average pressure in September - Mill Valley, CA
  • Average pressure in September: 29.92"

The month with the highest atmospheric pressure is January (30.13").
Months with the lowest atmospheric pressure are June, August and September (29.92").

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Average wind speed in September
Mill Valley, CA

Average wind speed in September - Mill Valley, CA
  • Average wind speed in September: 5.9mph

The windiest month (with the highest average wind speed) is May (7.8mph).
The calmest months (with the lowest average wind speed) are October and November (5.5mph).

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Average humidity in September
Mill Valley, CA

Average humidity in September - Mill Valley, CA
  • Average humidity in September: 71%

The month with the highest relative humidity is March (77%).
The month with the lowest relative humidity is October (68%).

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Average rainfall in September
Mill Valley, CA

Average rainfall in September - Mill Valley, CA
  • Average rainfall in September: 0.04"

The wettest month (with the highest rainfall) is February (0.87").
The driest months (with the least rainfall) are June, July, August and September (0.04").

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Average rainfall days in September
Mill Valley, CA

Average rainfall days in September - Mill Valley, CA
  • Average rainfall days in September: 1.7 days

The month with the highest number of rainy days is March (8.8 days).
Months with the least rainy days are June and August (1.2 days).

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Average daylight in September /
Average sunshine in September
Mill Valley, CA

Average daylight in September / Average sunshine in September - Mill Valley, CA
  • Average daylight in September: 12.4h

The month with the longest days is June (Average daylight: 14.8h).
The month with the shortest days is December (Average daylight: 9.6h).

  • Average sunshine in September: 10.4h

The month with the most sunshine is July (Average sunshine: 11.2h).
The month with the least sunshine is December (Average sunshine: 5.5h).

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Average sunshine days in September
Mill Valley, CA

Average sunshine days in September - Mill Valley, CA
  • Average sunshine days in September: 26 days

The month with the most sunshine days is June (26.4 days).
The month with the least sunshine days is March (20.7 days).

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Average UV index in September
Mill Valley, CA

Average UV index in September - Mill Valley, CA
  • Average UV index in September: 5

Months with the highest UV index are April, June, July, August and September (UV index 5).
Months with the lowest UV index are January, February, November and December (UV index 3).

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Average cloud cover in September
Mill Valley, CA

Average cloud cover in September - Mill Valley, CA
  • Average cloud cover in September: 19

The month with the most cloud cover is March (Cloud cover 39).
The month with the least cloud cover is September (Cloud cover 19).

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Average visibility in September
Mill Valley, CA

Average visibility in September - Mill Valley, CA
  • Average visibility in September: 6mi

Months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
Months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).

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